Problem: Using the van't Hoff factors in the table below, calculate the mass of solute required to make each aqueous solution.Van't Hoff factors at 0.05 m concentration in aqueous solutionSoluteExpectedMeasuredNonelectrolyte11NaCl21.9MgSO421.3MgCl232.7K2SO432.6FeCl343.4Calculate the mass of solute required to make a sodium chloride solution containing 161 g of water that has a melting point of -1.9 oC.

Recall that the freezing point of a solution is lower than that of the pure solvent and the change in freezing point (ΔT­_f) is given by:

$\boxed{{\mathbf{\Delta T}}_{\mathbf{f}}\mathbf{=}{\mathbf{T}}_{\mathbf{f}\mathbf{,}\mathbf{ }\mathbf{pure}\mathbf{ }\mathbf{solvent}}\mathbf{-}{\mathbf{T}}_{\mathbf{f}\mathbf{,}\mathbf{ }\mathbf{solution}}}$

The change in freezing point is also related to the molality of the solution:

$\boxed{{\mathbf{\Delta T}}_{\mathbf{f}}\mathbf{=}{\mathbf{imK}}_{\mathbf{f}}}$

where: 

i = van’t Hoff factor

m = molality of the solution (in m or mol/kg)

K_f = freezing point depression constant (in ˚C/m)

Recall that the molality of a solution is given by:

$\boxed{\mathbf{molality}\mathbf{=}\frac{\mathbf{moles}\mathbf{ }\mathbf{solute}}{\mathbf{kg}\mathbf{ }\mathbf{solvent}}}$